Thank you for the opportunity to assist you. I'm sorry for what you're going through.
You've already taken one step that I'd recommend - calling adult protective services. They investigate and take action on elder abuse cases, similar to the way child protective services does with children. Don't give up on this option. Keep reporting if you feel that's necessary or they're dragging their feet.
Another step is to go to your local court or to a family law attorney and inquire about obtaining guardianship or conservatorship over Ms. Jones. Being a guardian or conservator is different than having power of attorney. A guardian or conservator legally "becomes" the person who is the subject being conserved, in this case, Ms. Jones. If you were Ms. Jones' guardian or conservator, you could immediately move her away from Julie and Michael and cut J & M off from all aspects of Ms. Jones' life, including her money.
Finally, there may be a criminal case against Julie and Michael for embezzlement. If they are essentially stealing money from or defrauding an incapacitated person, that could be a crime. They may be committing other crimes, too, such as assault (yelling at Ms. Jones) or kidnapping her (not allowing her to move freely about and go where she wants.) Don't call 911 with this issue unless you have solid information that Ms. Jones is in immediate danger. Instead, call your local police or sheriff's office and make an appointment to speak to a detective. Tell them your concerns. They may or may not investigate the case and bring charges. You could also talk to the local prosecutor as well and express your concerns. He or she could ask the police to investigate if it appears that a crime may have occurred.
Thanks again for the opportunity to assist you. Please let me know if you need clarification. I'll get back to you as quickly as I can, although I may not be online at the moment you respond. Otherwise, I hope you'll rate my answer positively as it is the ONLY way I receive credit for my work and doing so will NOT cost you any additional fee.